Light emitting device and method for manufacturing the same

ABSTRACT

By using a light emitting device including an insulating substrate and a light emitting unit formed on the insulating substrate, the light emitting unit including: a plurality of linear wiring patterns disposed on the insulating substrate in parallel with one another, a plurality of light emitting elements that are mounted between the wiring patterns while being electrically connected to the wiring patterns, and a sealing member for sealing the light emitting elements, as well as a method for manufacturing thereof, it becomes possible to provide a light emitting device that achieves sufficient electrical insulation and has simple manufacturing processes so that it can be manufactured at a low cost, and a method for manufacturing the same.

This application is a continuation of U.S. patent application Ser. No.15/015,903 filed Feb. 4, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/245,974 filed Apr. 4, 2014, now U.S. Pat. No.9,484,502, which is a continuation of U.S. patent application Ser. No.13/786,393 filed Mar. 5, 2013, now U.S. Pat. No. 8,841,838, which is adivisional of U.S. patent application Ser. No. 12/916,048 filed Oct. 29,2010, now U.S. Pat. No. 8,427,048, which is a continuation applicationof U.S. patent application Ser. No. 12/049,690, filed Mar. 17, 2008, nowU.S. Pat. No. 7,843,131, which is based on and claims the priority ofJapanese Patent Application No. 2007-067362 filed with the Japan PatentOffice on Mar. 15, 2007, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a light emitting device and a methodfor manufacturing the same.

Description of the Background Art

In recent years, LEDs have come to be used frequently as light sourcesfor illumination apparatuses. Methods for obtaining white light in theillumination apparatus using LEDs include, for example, a method usingthree kinds of LEDs, that is, a red LED, a blue LED, and a green LED,and a method utilizing a fluorescent material that converts excitedlight from a blue LED to emit yellow light. With respect to the lightsources for illumination apparatuses, since white light havingsufficient luminance is required, illumination apparatuses using aplurality of LED chips have been commercialized.

For one example of such an illumination apparatus, Japanese PatentLaying-Open No. 2003-152225 (Patent Document 1) discloses a lightemitting device 101 as schematically shown in FIG. 14. Light emittingdevice 101 shown in FIG. 14 has a structure in which element storageunits 103, each having a concave shape, are formed on a metal plate 102made of aluminum, and a printed circuit board 104, which is aninsulating glass epoxy substrate with a wiring unit 105 made of copperfoil being placed thereon, is formed between the element storage units.Moreover, in the example shown in FIG. 14, a light emitting element 106,placed (disposed) on each element storage unit 103, and wiring unit 105on printed circuit board 104 are electrically connected with each otherthrough a bonding wire 107. Furthermore, these element storage units 103are sealed by a resin sealing member 108 in such a manner as to coverall light emitting device 106 and bonding wire 107. Patent Document 1describes that, with this structure, it is possible to provide a lightemitting device that improves the heat radiating property and is capableof effectively taking out light to the outside from the light emittingdiode chip.

However, in light emitting device 101 shown in FIG. 14, printed circuitboard 104, with wiring unit 105 made of copper foil being formedthereon, is disposed in the immediate vicinity of metal plate 102 madeof aluminum (in the Figure, a linear distance d with respect to thehorizontal direction is shown as a distance between metal plate 102 andwiring unit 105). For this reason, the resulting assumption is thatsufficient electrical insulation is not achieved between metal plate 102and wiring unit 105. Moreover, since light emitting device 101 as shownin FIG. 14 has printed circuit board 104 formed of a glass epoxysubstrate, complicated manufacturing processes are required, therebyfailing to provide a light emitting device at a low cost.

For example, Japanese Patent Laying-Open No. 2006-287020 (PatentDocument 2) discloses a LED member 201 as schematically shown in FIG.15. LED member 201 shown in FIG. 15 has a structure in which a heatradiating plate 203 made of metal or ceramics, with a LED chip 204 beingmounted thereon, is joined in a through hole formed in a wiring board202. In the example shown in FIG. 15, LED chip 204 and a wiring pattern205 formed in wiring board 202 are electrically connected with eachother by a bonding wire W, and these LED chip 204 and bonding wire W areembedded with a resin sealing member 206 made of a transparent resin.Patent Document 2 describes that, with this structure, the heatgeneration of the LED chip is effectively released, so that it becomespossible to provide a surface-packaging type LED member with goodproductivity, and a method for manufacturing the same.

In Patent Document 2, however, no detailed description is given as tothe method for applying the transparent resin used for embedding LEDchip 204 and bonding wire W. Moreover, in LED member 201 shown in FIG.15 of Patent Document 2, since wiring pattern 205 is formed on sidefaces of wiring board 202 as well as on one portion of the back face, itis difficult to manufacture such a structure, resulting in a failure tomanufacture the member at a low cost.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-mentionedproblems, and its object is to provide a light emitting device thatachieves sufficient electrical insulation, and has simple manufacturingprocesses so that it can be manufactured at a low cost, and a method formanufacturing the same.

A light emitting device in accordance with the present invention is alight emitting device including an insulating substrate and a lightemitting unit formed on the insulating substrate, characterized in thatthe light emitting unit has a plurality of linear wiring patternsdisposed on the insulating substrate in parallel with one another, aplurality of light emitting elements that are mounted between the wiringpatterns while being electrically connected to the wiring patterns, anda sealing member for sealing the light emitting elements.

In the light emitting device of the present invention, more than onelight emitting elements are preferably mounted with each of the linearwiring patterns being sandwiched therebetween, to be linearly alignedalong the wiring patterns. Moreover, the light emitting elements mountedwith each of the linear wiring patterns being sandwiched therebetweenare preferably disposed in a mutually shifted state so as not to allowside faces thereof to oppose one another.

Moreover, in the light emitting device of the present invention, thelight emitting elements each of which has a rectangular shape in topview are preferably mounted such that a direction along a short sidethereof is parallel with a longitudinal direction of the wiringpatterns, and more preferably, each of the light emitting elements hasan elongated shape in top view.

In the light emitting device of the present invention, preferably, thelight emitting elements mounted with each of the linear wiring patternsbeing sandwiched therebetween are electrically connected in series withone another. More preferably, the light emitting elements linearlymounted along the linear wiring patterns are electrically connected inparallel with one another.

In the light emitting device of the present invention, preferably, thewiring patterns further include a pattern for positioning electricalconnections between the light emitting elements, or a pattern serving asa measure for mounting positions of the light emitting elements.

In the light emitting device of the present invention, a linear distancebetween each light emitting element and each wiring pattern ispreferably 0.1 mm or more.

In the light emitting device of the present invention, the insulatingsubstrate is preferably formed of a white ceramic substrate, and thewhite ceramic substrate is made of any material selected from aluminumoxide, aluminum nitride, boron nitride, silicon nitride, magnesiumoxide, forsterite, steatite and low-temperature sintered ceramics, or acomposite material of these materials.

In the light emitting device of the present invention, the linear wiringpatterns and light emitting elements on the insulating substrate arepreferably sealed by a single sealing member.

Moreover, in the light emitting device of the present invention, thesealing member preferably contains a fluorescent material, and thesealing member more preferably includes a first sealing member layercontaining a first fluorescent material and a second sealing memberlayer that contains a second fluorescent material and is laminated onthe first sealing member layer. In this case, the second sealing memberlayer is preferably laminated on the first sealing member layer so as tocover at least one portion of the first sealing member layer.

In the light emitting device of the present invention, the sealingmember is preferably formed into a hexagonal shape, a round shape, arectangular shape, or a square shape in top view.

Moreover, the light emitting device of the present invention ispreferably formed into a round shape or a square shape in top view.

The light emitting device of the present invention is preferably usedfor a backlight light source of a liquid crystal display or a lightsource for illumination.

The present invention also provides a method for manufacturing a lightemitting device including the steps of: forming wiring patterns on aninsulating substrate; mounting a light emitting element between thewiring patterns; electrically connecting the light emitting element andthe wiring patterns; placing a silicone rubber sheet having a throughhole onto the insulating substrate; and forming a sealing member forsealing the light emitting element in the through hole of the siliconerubber sheet.

The method for manufacturing a light emitting device of the presentinvention preferably further includes the steps of: inspecting acharacteristic of the light emitting element after electricallyconnecting the light emitting element with the wiring patterns; and upondetection of any defect in characteristics as a result of theinspection, connecting a spare light emitting element with the wiringpatterns.

In the method for manufacturing a light emitting device of the presentinvention, the sealing member preferably contains a fluorescentmaterial. In this case, in the method for manufacturing a light emittingdevice of the present invention, the step of sealing the light emittingelements by using the sealing member preferably includes the steps of:injecting a sealing material containing a first fluorescent materialinto the through hole of the silicone rubber sheet; curing the sealingmaterial containing the first fluorescent material to form a firstsealing member layer; and measuring a chromaticity characteristic of thelight emitting device after the first sealing member layer is formed.Moreover, in the method for manufacturing a light emitting device of thepresent invention, the step of sealing the light emitting element byusing the sealing member preferably includes the steps of: after thestep of measuring a chromaticity characteristic of the light emittingdevice after the first sealing member layer is formed, injecting asealing material containing a second fluorescent material onto the firstsealing member layer; curing the sealing material containing the secondfluorescent material to form a second sealing member layer; measuring achromaticity characteristic of the light emitting device after thesecond sealing member layer is formed; and removing the silicone rubbersheet.

In accordance with the present invention, it becomes possible to providea light emitting device that achieves sufficient electrical insulation,and has simple manufacturing processes so that it can be manufactured ata low cost, and a method for manufacturing the same. Moreover, the lightemitting device of the present invention has an improved color renderingproperty in comparison with conventional devices, and is less likely tocause color shifts; therefore, it is suitably applicable to a liquidcrystal display and a light source for illumination.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view schematically showing a light emitting device 1 inaccordance with a first preferred example of the present invention.

FIG. 2 is a cross-sectional view schematically showing a light emittingunit 2 in light emitting device 1 of the example shown in FIG. 1.

FIG. 3 is a top view schematically showing an insulating substrate 3 inlight emitting device 1 of the example shown in FIG. 1.

FIG. 4 is a top view schematically showing a light emitting device 21 inaccordance with a second preferred example of the present invention.

FIG. 5 is a top view schematically showing a light emitting device 31 inaccordance with a third preferred example of the present invention.

FIG. 6 is a top view schematically showing a light emitting device 41 inaccordance with a fourth preferred example of the present invention.

FIG. 7 is a top view schematically showing a light emitting device 51 inaccordance with a fifth preferred example of the present invention.

FIG. 8 is a perspective view illustrating a case in which light emittingdevice 1 of the example shown in FIG. 1 is applied to a fluorescentlighting-type LED lamp 61.

FIG. 9 is a perspective view illustrating a case in which light emittingdevice 41 of the example shown in FIG. 6 is applied to a fluorescentlighting-type LED lamp 71.

FIG. 10 is a perspective view illustrating a case in which lightemitting device 41 of the example shown in FIG. 6 is applied to a lightbulb-type LED lamp 81.

FIG. 11 is a diagram showing step by step a preferred example of amanufacturing method for a light emitting device of the presentinvention.

FIG. 12 is a diagram schematically showing a silicone rubber sheet 91 inaccordance with a preferred example, which is used for the method formanufacturing a light emitting device of the present invention.

FIG. 13 is a graph showing chromaticity coordinates of CIE.

FIG. 14 is a cross-sectional view schematically showing a typicalconventional light emitting device 101.

FIG. 15 is a cross-sectional view schematically showing a typicalconventional LED member 201.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a top view of a light emitting device 1 in accordance with afirst preferred example of the present invention, and FIG. 2 is across-sectional view schematically showing a light emitting unit 2 inlight emitting device 1 of the example shown in FIG. 1. FIG. 3 is a topview schematically showing an insulating substrate 3 in light emittingdevice 1 of the example shown in FIG. 1. Light emitting device 1 of thepresent invention has a structure in which a plurality of linear wiringpatterns 4 are formed on an insulating substrate 3 in parallel with oneanother, with a plurality of light emitting elements 5 being mountedbetween wiring patterns 4 while being electrically connected to wiringpatterns 4, and is provided with a light emitting unit 2 sealed by asealing member 6. In particular, light emitting device 1 of the presentinvention makes it possible to increase a dielectric voltage between theadjacent light emitting elements as well as between the light emittingelements and the electrodes, by directly mounting light emittingelements 5 onto insulating substrate 3.

In accordance with light emitting device 1 of the present invention,between linear wiring patterns 4 that are formed on insulating substrate3, the plurality of light emitting elements 5 that are electricallyconnected to wiring patterns 4 are mounted so that, unlike aconventional structure in which an insulating layer having wiring uniton printed circuit board is formed on a metal substrate, a sufficientelectrical insulating property is achieved. That is, as described above,in the structure as shown in the conventional example of FIG. 14, sincea printed circuit board 104 with a wiring unit 105 formed thereon isdisposed in the immediate vicinity of a metal plate 102 on which thelight emitting elements are mounted, it is difficult to achievesufficient electrical insulation. In this structure, in order to achievesufficient electrical insulation without the necessity of isolation byusing an insulating material, it is necessary to ensure a sufficientlength for a linear distance d in the horizontal direction between metalplate 102 and wiring unit 105. In contrast, in light emitting device 1of the present invention, since wiring patterns 4 are directly formed oninsulating substrate 3, and light emitting elements 5 are directlymounted on insulating substrate 3 so that light emitting elements 5 andwiring patterns 4 are electrically connected through a bonding wire W;thus, the light emitting device can be designed without the necessity oftaking into consideration the above-mentioned linear distance, and themanufacturing processes can be carried out easily. Moreover, in lightemitting device 1 of the present invention, since the structure does notrequire forming of an insulating layer on the metal plate, it ispossible to omit the process for forming an insulating layer on a metalplate in manufacturing, and consequently to make the manufacturingprocesses more easier from this viewpoint as well.

Moreover, in the case where a light emitting device with a single lightemitting element having strong light emitting intensity is allowed toemit light, light emission in the form of a bright spot is given, withthe result that, since it is dazzling to human eyes, the applicationthereof is limited. In light emitting device 1 of the present invention,since a plurality of light emitting elements 5 are provided, it ispossible to achieve uniform light emission without causing the lightemission in the form of a bright spot, and consequently to make itusable for a wide range of applications. Furthermore, in light emittingdevice 1 of the present invention, along each of a plurality of linearwiring patterns 4 that are formed in parallel with one another, mountingpositions of a plurality of light emitting elements 5 can be freely setas needed, so that the luminance adjustment and chromaticity adjustmentof light emitting device 1 can be easily carried out. Moreover, in thislight emitting device 1, the mounting positions of light emittingelements 5 can be set such that the heat generation of the lightemitting elements is not concentrated, thereby making it possible toprovide an appropriate heat releasing measure. Moreover, since lightemitting device 1 of the present invention makes it possible to adjustthe number of light emitting elements to be mounted, all the lightfluxes and the power consumption can be adjusted in accordance withdesired specifications.

In light emitting device 1 of the present invention, the plurality oflight emitting elements 5 are preferably mounted linearly along eachwiring pattern so as to allow each linear wiring pattern to besandwiched between light emitting elements 5. With respect to the numberof the wiring patterns in the light emitting device of the presentinvention, although not particularly limited, since one or more anodewiring patterns and cathode wiring patterns are required, at least twoor more wiring patterns are required, so that the number is preferablywithin a range from two to four. In order to obtain all the light fluxesof 300 lm from the light emitting device at the time of an electriccurrent of 350 mA, thirty-six light emitting elements are required. Inthis case, wiring patterns 4 are prepared to include four wiringpatterns 4 a, 4 b, 4 c and 4 d, and twelve light emitting elements 5 aremounted between wiring patterns 4 a and 4 b, twelve of them are mountedbetween wiring patterns 4 b and 4 c, and twelve of them are also mountedbetween wiring patterns 4 c and 4 d (examples shown in FIGS. 1 to 3).

It should be noted that FIGS. 1 to 3 show examples in which lightemitting device 1 has a square top shape, and in this case, as shown inFIG. 3, linear wiring patterns 4 are preferably formed so as to beparallel to one of the diagonal lines of the square shape that is a topshape of light emitting device 1. By forming wiring patterns 4 in thismanner, the lengths and intervals of wiring patterns 4 can be ensuredsufficiently, and areas used for forming securing holes, external wiringholes and the like of the light emitting device, which will be describedlater, can also be ensured advantageously. It should be noted that theabove-mentioned top shape of the light emitting device refers to a shapeof insulating substrate 3 on a cross section in parallel with thesubstrate face.

Moreover, in light emitting device 1 of the present invention,respective light emitting elements 5 mounted with each wiring pattern 4being sandwiched therebetween are preferably disposed in a shiftedmanner so that the side faces thereof do not oppose one another. FIG. 2shows an example in which respective light emitting element 5 mountedwith each wiring pattern 4 being sandwiched therebetween are disposed sothat the side faces thereof oppose one another, and FIG. 3 shows anexample in which said light emitting element 5 are disposed so that theside faces thereof do not oppose one another. By disposing lightemitting elements 5 as shown in the example of FIG. 3, advantages suchas a uniform luminance and reduction in luminance irregularities can beobtained.

Moreover, in light emitting device 1 of the present invention, a lightemitting element 5 having a rectangular shape in top view is preferablyused. The top shape of light emitting element 5 herein refers to a shapeon a top view in parallel with the substrate face of insulatingsubstrate 3 in a mounted state on insulating substrate 3. With respectto light emitting element 5 having a rectangular shape in top view,specifically, a light emitting element having a short side in a range of200 to 300 μm and a long side in a range of 400 to 1000 μm in the topshape is exemplified. In the light emitting device of the presentinvention, when light emitting elements 5 having such a rectangularshape in top view are used, light emitting elements 5 are preferablymounted in such a manner as to make the direction along the short sideof the top shape of each of light emitting elements 5 in parallel withthe longitudinal direction of wiring patterns 4. Normally, each lightemitting element 5 having a rectangular shape in top view has itselectrode pad formed on the upper face on one of the short sides;therefore, by mounting light emitting elements 5 in the above-mentionedmanner, the electrical connection between the electrode pad of lightemitting element 5 and wiring pattern 4 by the use of a bonding wire Wcan be easily carried out, so that it becomes possible to preventdefects such as cutting of bonding wire W and peeling of bonding wire W.Moreover, with this arrangement, a desired number of light emittingelements 5 can be mounted at desired intervals along the longitudinaldirection of wiring patterns 4, so that it becomes possible to easilycarry out adjustment to obtain desired light.

As described above, light emitting element 5 having a rectangular shapein top view is preferably used in light emitting device 1 of the presentinvention, and normally, by forming the electrode pad on one of theshort sides on the upper face of each light emitting element asdescribed above, light emitting element 5 is easily electricallyconnected to wiring pattern 4 using bonding wire W; thus, since theeffects of preventing defects such as cutting and peeling of bondingwire W are prominent, light emitting element 5 having an elongated topshape is preferably used for light emitting device 1 of the presentinvention. The “elongated shape” herein refers to a shape in which, in atop shape, the length of a long side is conspicuously long with respectto the length of a short side, and, for example, a light emittingelement having a top shape with 480 μm-long side and 240 μm-short sideis exemplified. In the case where a light emitting element having theelongated top shape is used, the light emitting element, in whichelectrode pads are provided on both of the short sides on the upper faceso as to oppose one another, is preferably used.

In light emitting device 1 of the present invention, how to electricallyconnect the linear wiring patterns 4 disposed in parallel with oneanother and light emitting elements 5 is not particularly limited, andlight emitting elements 5 mounted with each linear wiring pattern 4sandwiched therebetween may be electrically connected in series with oneanother, or may be electrically connected in parallel with one another.Light emitting elements 5 mounted with each linear wiring pattern 4sandwiched therebetween may be electrically connected in series with oneanother, and light emitting elements 5 linearly mounted along the linearwiring patterns may be electrically connected in parallel with oneanother. It should be noted that the distance between the light emittingelement and the electrode is preferably made closer because the closerthe distance is, the smaller the voltage drop due to the resistance ofthe wiring becomes. Further, with respect to the light emitting elementslinearly disposed along each wiring pattern, preferably, all of them arenot electrically connected to electrodes, with some of the lightemitting elements being merely mounted as spare light emitting elements.With this arrangement, in the case where some of the light emittingelements are found to be defective that do not emit light in aninspection process (which will be described later) prior to a sealingprocess of the light emitting elements by a sealing member, the sparelight emitting elements can be electrically connected to the electrodesso as to ensure predetermined brightness.

Moreover, in the light emitting device of the present invention, thewiring patterns preferably further include a positioning pattern for usein electrical connection to the light emitting elements or a patternserving as a measure for mounting positions of the light emittingelements. FIG. 3 shows an example in which patterns 7 are formed asdots, and connected to four linear wiring patterns 4 formed in parallelwith one another. These patterns 7 can be used as positioning patternsfor electrical connection between wiring patterns 4 and light emittingelements 5, or as a measure for mounting positions of light emittingelements 5, so that the mounting process of the light emitting elementsand the electrical connections thereof to the wiring patterns can befacilitated, and there is obtained another advantage that these patternscan also be used as recognition patterns when an automation apparatus isused.

In light emitting device 1 of the present invention, the linear distancebetween each light emitting element 5 and each wiring pattern 4 ispreferably 0.1 mm or more, more preferably, to 0.5 mm or more. Thelinear distance here refers to a linear distance between each lightemitting element 5 and each wiring pattern 4 in a direction along thesubstrate face of insulating substrate 3. By setting the linear distanceto 0.1 mm or more, it is possible to positively ensure the electricalinsulating property. It should be noted that from the viewpoint ofpreventing the dropping at the time of wire bonding and cutting of thebonding wire, the linear distance between each light emitting element 5and each wiring pattern 4 is preferably 1.5 mm or less, more preferably,to 1.0 mm or less.

As shown in FIG. 2, light emitting device 1 of the present invention ispreferably designed such that the thickness of wiring pattern 4 issmaller than the thickness of light emitting element 5. With thisarrangement, it is possible to reduce shielding of the light emittedfrom light emitting elements 5 with the light released to the outside bythe wiring patterns, and consequently to achieve a light emitting device1 capable of efficiently emitting light to the outside. Morespecifically, the difference between the thickness of theabove-mentioned area of each wiring pattern 4 and the thickness of lightemitting element 5 is preferably 0.005 mm or more, more preferably, 0.07mm or more.

It is only necessary for insulating substrate 3 in light emitting device1 of the present invention to be formed with a material having aninsulating property, and although not particularly limited, a whiteceramic substrate is preferably used because of its small thermalexpansion, high heat conductivity and high light reflectance. The “whitecolor” here refers to a color of an object that allows the object toreflect virtually 100% of all the wavelengths of visible light rays(however, no such an ideal white color object having a reflectance of100% exists). By using a white color ceramic substrate as insulatingsubstrate 3, among outgoing light rays from light emitting elements 5,particularly those light rays proceeding toward the lower face can bereflected by the white color ceramic substrate, so that outgoing lightrays from light emitting elements 5 can be effectively utilized withoutlosses, and the resulting light emitting elements 5 can be suitably usedfor applications that require a high heat radiating property and a heatresistant property, and supply a large electric current as a drivingelectric current. Moreover, it becomes possible to improve reliabilityof light emitting elements 5, and in the case where sealing member 6contains a fluorescent material (which will be described later), it alsobecomes possible to suppress degradation in the fluorescent material dueto heat from light emitting elements 5, so that it is possible to makethe light rays to be wavelength-converted and released from thefluorescent material less likely to cause chromaticity shifts.Furthermore, since the use of the ceramic substrate having a high lightreflectance as described above eliminates the necessity of using silverhaving a light reflectance of 90% or more as the substrate materialand/or the forming material for the wiring patterns, neither problem ofsilver migration nor sulfurized silver occurs.

When using the white color ceramic substrate, since a high level lightreflectance, that is, 90% or more, is required, the material ispreferably selected from aluminum oxide (alumina), aluminum nitride,boron nitride, silicon nitride, magnesium oxide, forsterite, steatite,and low-temperature sintered ceramics, or a ceramic substrate formed ofa composite material of these materials is preferably used. Among these,a white ceramic substrate made of aluminum oxide (alumina) that isinexpensive, has high reflectance, is easily processed, and is widelyused as an industrial material, is preferably used.

With respect to light emitting elements 5 to be used for light emittingdevice 1 of the present invention, light emitting elements that arenormally used in the corresponding field can be used withoutlimitations. Examples of such a light emitting element includesemiconductor light emitting elements, such as a blue-color-based LED(light emitting diode) chip, an InGaAlP-based compound semiconductor LEDchip, and an AlGaAs-based compound semiconductor chip, made by growing amaterial such as a gallium nitride-based compound semiconductor and aZnO (zinc oxide)-based compound semiconductor on a substrate such as asapphire substrate, a ZnO (zinc oxide) substrate, a GaN substrate, a Sisubstrate, a SiC substrate, and a spinel substrate. Among these, since aone-sided structure with two electrodes is easily formed on aninsulating substrate and since a nitride semiconductor having superiorcrystallinity can be formed with high mass productivity, ablue-color-based LED made by growing a gallium nitride-based compoundsemiconductor on a sapphire substrate is preferably used as a lightemitting element. In the case where such a blue-color-based LED is usedas the light emitting element, a light emitting device is preferablydesigned so as to obtain white color by dispersing a fluorescentmaterial that is excited by light from the semiconductor light emittingelement to emit yellowish light in a sealing member (which will bedescribed later).

With respect to the light emitting elements used for the light emittingdevice of the present invention, the color of light emission is notlimited to a blue-color light emission, and light emitting elementshaving a light-emission color, such as an ultraviolet-ray light emissionand a green-color light emission, may of course be used. Moreover,another light emitting device may of course be achieved in which, inplace of the arrangement that, by using a blue-color-based LED as alight emitting element, light rays emitted from this blue-color-basedLED are converted by a fluorescent material to obtain white color, byusing three-colored LED chips of red, green, and blue as the lightemitting elements without using the fluorescent material, light rayshaving required colors such as white color for illumination, areobtained.

Although not particularly limited, the shape of light emitting elements5 used in light emitting device 1 of the present invention is preferablyprepared as a rectangular shape in top view, as described earlier, andmore preferably, as an elongated shape. It should be noted that in lightemitting device 1 of the present invention, each light emitting element5 in which a P-side electrode and an N-side electrode are formed on oneof the faces needs to be used. Such a light emitting element 5 ismounted between wiring patterns 4 on insulating substrate 3, with theface having the P-side electrode and the N-side electrode formed thereonas the upper face, and electrically connected to wiring patterns 4.

As shown in FIG. 2, the electrical connection between light emittingelements 5 and wiring patterns 4 is made by bonding the P-side electrodeand the N-side electrode to wiring patterns 4 through bonding wires W.With respect to the bonding wires W, any of metal thin wiresconventionally used in the corresponding field may be used withoutparticular limitations. Examples of the metal thin wires include a goldwire, an aluminum wire, a copper wire, and a platinum wire, and amongthese, the gold wire, which is less likely to corrode, good in moistureresistance, environmental resistance, adhesion, electrical conductivity,thermal conductivity, and elongation percentage, and easily formed intoa ball, is preferably used as bonding wire W.

The light emitting device 1 of the present invention has a structure inwhich a plurality of light emitting elements 5 mounted between wiringpatterns 4 while being electrically connected to wiring patterns 4 asdescribed above are sealed by a sealing member 6 together with bondingwires W that make the electrical connection. The sealing process bysealing member 6 may be carried out by forming a plurality of linearsealing members so as to contain light emitting elements 5 mounted alongthe two sides of each linear wiring pattern 4, or may be carried out bysealing all the linear wiring patterns and light emitting elements onthe insulating substrate by using one sealing member. From theviewpoints of reducing luminescence irregularities of the light emittingdevice and of reducing variation in the thickness of the sealing member,as shown in examples of FIGS. 1 to 3, it is preferable to seal all thelinear wiring patterns and light emitting elements on the insulatingsubstrate by using one sealing member.

The material (sealing material) used for forming sealing member 6 inlight emitting device 1 of the present invention is not particularlylimited, and any of materials conventionally widely known in thecorresponding field may appropriately be used as long as it is amaterial having a light-transmitting property. Examples of the sealingmaterial include light-transmitting resin materials having superiorweather resistance, such as an epoxy resin, a urea resin and a siliconeresin, and light-transmitting inorganic materials having superiorresistance to light, such as silica sol and glass.

Sealing member 6 in the present invention is preferably contain afluorescent material so as to be adjustable to obtain desirable lightand to easily obtain white color, neutral white color, incandescent lampcolor, and the like. Preferable examples of the fluorescent materialinclude: Ce:YAG (cerium-activated yttrium-aluminum-garnet) fluorescentmaterial, Eu:BOSE (europium-activated strontium-barium-orthosilicate)fluorescent material, and europium-activated α-sialon fluorescentmaterial; however, the present invention is not intended to be limitedthereto.

It should be noted that sealing member 6 of the present invention maycontain a dispersing agent together with the fluorescent material.Although not particularly limited, preferable examples of the dispersingagent include barium titanate, titanium oxide, aluminum oxide, siliconoxide, calcium carbonate and silicon dioxide.

Sealing member 6 in the present invention can be achieved by using twolayers in accordance with the chromaticity of desired light for lightemitting device 1. In this case, as shown in FIG. 2, the structure ispreferably designed to have a first sealing member layer 8 containing afirst fluorescent material and a second sealing member layer 9containing a second fluorescent material that is laminated on firstsealing member layer 8. By forming sealing member 6 using first sealingmember layer 8 and second sealing member layer 9 in this manner, itbecomes possible to provide a light emitting device in which thechromaticity may be easily adjusted and which is free from chromaticityshifts can advantageously be provided at a low cost with a high yield.Desirable specific examples include processes in which methyl siliconeis used as a resin material, and Eu:BOSE is dispersed therein as a firstfluorescent material to be cured to form first sealing member layer 8,and organic modified silicone is used as a resin material so as to coverthis first sealing member layer 8, and Eu:SOSE is dispersed therein as asecond fluorescent material to be cured to form second sealing memberlayer 9. From the viewpoint of adjusting colors for correctingchromaticity shifts, second sealing member layer 9 is preferablylaminated on first sealing member layer 8 so as to cover at least oneportion of the upper face of first sealing member layer 8, and as shownin FIG. 2, more preferably, the structure is preferably achieved bycovering the entire upper face of first sealing member layer 8 withsecond sealing member layer 9. In the case where a light emitting devicethat emits light having desired chromaticity is obtained with only onelayer (first fluorescent material layer), sealing member 6 may of coursebe formed in a single layer. The border between first sealing materiallayer 8 containing the first fluorescent material and second sealingmaterial layer 9 containing the second fluorescent material may beclearly separated from each other, or need not be clearly separated fromeach other.

Although not particularly limited, the shape of sealing member 6 of thepresent invention is preferably a hexagonal shape, a round shape, arectangular shape or a square shape in top view. For example, FIGS. 1 to3 show examples in which first sealing member layer 8 is formed into asquare shape in top view, with second sealing member layer 9 having asquare shape in top view being formed so as to cover the entire upperface of first sealing member layer 8. It should be noted that the topshapes of the above-mentioned sealing member 6, first sealing memberlayer 8, and second sealing member layer 9 refer to the shape on a crosssection in parallel with the substrate face of insulating substrate 3.

FIG. 4 is a top view showing a light emitting device 21 in accordancewith a second preferred example of the present invention. In the exampleof FIG. 4, light emitting device 21 has the same structure as that oflight emitting device 1 shown in the example of FIG. 1 except that thetop shape of a sealing member 22 is a round shape; therefore, thosemembers having similar structures are indicated by the same referencenumerals, and the description thereof is omitted. As shown in FIG. 4,since sealing member 22 is designed to have a round top shape, theresulting symmetrical shape advantageously provides good lightdirectivity. For this reason, among the above-mentioned hexagonal shape,round shape, rectangular shape, and square shape, as shown in FIG. 4,sealing member 22 is in particular preferably designed to have a roundtop shape.

Moreover, the sealing member 6 may be formed into a semi-spherical shapewith an upward convex portion. In this case, sealing member 6 is allowedto have a function as a lens.

Although not particularly limited, the entire shape of light emittingdevice 1 of the present invention is preferably designed to have ahexagonal shape, a round shape, a rectangular shape or a square shape intop view. In the case where the light emitting device has a rectangularor square top shape, since the light emitting device can be disposed ina tightly contact state, the resulting light emitting device can besuitably applied to a fluorescent lighting-type LED lamp. Moreover, inthe case where the light emitting device is applied to a light-bulb-typeLED lamp (which will be described later), the light emitting device ispreferably designed to have a round top shape. FIGS. 1 and 4 showexamples in which light emitting device 1 is designed to have a squaretop shape, as described above.

FIG. 5 is a top view showing a light emitting device 31 in accordancewith a third preferred example of the present invention. In the exampleof FIG. 5, light emitting device 31 has the same structure as that oflight emitting device 1 shown in the example of FIG. 1 except that thetop shape of a sealing member 33 is a hexagonal shape and that the topshape of light emitting device 31 is a round shape; therefore, thosemembers having similar structures are indicated by the same referencenumerals, and the description thereof is omitted. As in light emittingdevice 31 shown in the example of FIG. 5, since sealing member 33 isdesigned to have a hexagonal top shape, the resulting symmetrical shapeadvantageously provides good light directivity. Moreover, as shown inthe example of FIG. 5, light emitting device 31 having a round top shape(using an insulating substrate 32 having a round top shape) is suitablyapplicable to a light-bulb-type LED lamp.

FIG. 6 is a top view showing a light emitting device 41 in accordancewith a fourth preferred example of the present invention. In the exampleof FIG. 6, light emitting device 41 has the same structure as that oflight emitting device 31 shown in the example of FIG. 5 except that thetop shape of a sealing member 42 (first sealing member layer 43) is around shape and that a second sealing member layer 44 is formed in sucha manner as to cover only one portion of the upper face of first sealingmember layer 43; therefore, those members having similar structures areindicated by the same reference numerals, and the description thereof isomitted. As shown by light emitting device 41 in the example of FIG. 6,since sealing member 42 is designed to have a round top shape, theresulting symmetrical shape advantageously provides good lightdirectivity. Moreover, in the example of FIG. 6, first sealing memberlayer 43 formed to have a round top shape and second sealing memberlayer 44 formed to partially cover first sealing member layer 43 formsealing member 42. By forming second sealing member layer 44 in such amanner as to partially cover first sealing member layer 43, only oneportion of the first sealing member layer can be adjusted so that alight emitting device having a desired chromaticity characteristic as alight emitting device (for example, within a range of (b) in FIG. 13indicating chromaticity coordinates, which will be described later) isadvantageously obtained. In this case, the portion of first sealingmember layer 43 to be covered by second sealing member layer 44 isselected in accordance with a desired chromaticity characteristic (forexample, on first sealing member layer 43, the portion that is notwithin the range of (b) in FIG. 13 indicating the desired chromaticitycoordinates to be described later, is covered by second sealing memberlayer 44). Moreover, in the case of light emitting device 41 in theexample shown in FIG. 6, since it has a round top shape, it is suitablyapplied to a light-bulb-type LED lamp in the same manner as lightemitting device 31 in the example shown in FIG. 5.

FIG. 7 is a top view showing a light emitting device 51 in accordancewith a fifth preferred example of the present invention. In the exampleof FIG. 7, light emitting device 51 has the same structure as that oflight emitting device 31 shown in the example of FIG. 5 except that thetop shape of a sealing member 52 (first sealing member layer 53) is asquare shape and that second sealing member layer 44 is formed in such amanner as to cover only one portion of the upper face of first sealingmember layer 53; therefore, those members having similar structures areindicated by the same reference numerals, and the description thereof isomitted. As shown by light emitting device 51 shown in the example ofFIG. 7, since sealing member 52 (first sealing member layer 53) isdesigned to have a square top shape, the resulting shape advantageouslyensures an area which allows a securing hole, an external wiring hole,and the like to be formed therein. Moreover, in the example of FIG. 7,first sealing member layer 53 formed to have a square top shape andsecond sealing member layer 44 formed to partially cover first sealingmember layer 53 form sealing member 52, and this structure exertssimilar effects to those of the example shown in FIG. 6. Moreover, inthe case of light emitting device 51 in the example shown in FIG. 7,since it has a round top shape, it is suitably applied to alight-bulb-type LED lamp in the same manner as light emitting devices 31and 41 in the examples shown in FIGS. 5 and 6. The above-mentioned firstsealing member layer 43 and first sealing member layer 53 contain afirst fluorescent material, and second sealing member layer 44 containsa second fluorescent material.

In accordance with the present invention, it is possible to provide alight emitting device that is easily manufactured, and is less likely toproduce color shifts. Such a light emitting device of the presentinvention can in particular suitably be used as a backlight light sourceof a liquid crystal display or a light source for illumination. By usingthe light emitting device of the present invention, it is possible toachieve the light source having any color tone including white color,such as a light bulb color.

In order to use for the above-mentioned application, the light emittingdevice of the present invention normally has securing holes used forattaching and securing to a matching member. In light emitting devices 1and 21 having a square top shape shown in FIGS. 1 and 4, one securinghole 11 formed to penetrate insulating substrate 3 is disposed along adiagonal line at each of the opposing corner portions of insulatingsubstrate 3 having a square shape in top view. Moreover, in lightemitting devices 31, 41 and 51 each having a round top shape shown inFIGS. 5 to 7, one securing hole 34 formed as a cut-out section is formedand disposed along each of straight lines passing through the center ofinsulating substrate 32 having a round shape in top view.

In order to use for the above-mentioned application, the light emittingdevice of the present invention is attached to a matching member to besecured thereto by using a securing jig. With respect to the securingjig, for example, a securing jig 19 as shown in FIGS. 1 and 4, which isa screw to be inserted into each securing hole 11 with a threaded innerwall and engaged therewith, is used. Moreover, the securing jig may beprepared as a bonding sheet or the like.

The light emitting device of the present invention is preferably securedby using a securing jig made of the same material as that of theinsulating substrate. By using the securing jig made of the samematerial as that of the insulating substrate, the thermal expansioncoefficient of the insulating substrate and the thermal expansioncoefficient of the securing jig are made equal to each other, so that itbecomes possible to prevent cracks and crevices from occurring in theinsulating substrate due to warping or the like by heat, andconsequently to improve the yield of the light emitting device. Morespecifically, any of materials selected from aluminum oxide, aluminumnitride, boron nitride, silicon nitride, magnesium oxide, forsterite,steatite, and low-temperature sintered ceramics, or a composite materialof these materials, is suitably used for the securing jig as well as forthe forming material for the insulating substrate.

FIGS. 8 to 10 show examples in which the light emitting device of thepresent invention is used as a light source for illumination. FIG. 8 isa perspective view illustrating a case in which light emitting device 1of the example shown in FIG. 1 is applied to a fluorescent lighting-typeLED lamp 61, FIG. 9 is a perspective view illustrating a case in whichlight emitting device 41 of the example shown in FIG. 6 is applied to afluorescent lighting-type LED lamp 71 (second fluorescent material layer44 partially covering first fluorescent material layer 43 is omitted),and FIG. 10 is a top view illustrating a case in which light emittingdevice 41 of the example shown in FIG. 6 is applied to a light bulb-typeLED lamp 81. As shown in FIGS. 8 to 10, light emitting devices 1 and 41are attached and secured through securing holes 11 and 34 respectively,by using securing jigs 19.

It should be noted that, as shown in each of FIGS. 1 and 4 to 7, thelight emitting device of the present invention is preferably designed tohave a structure in which a positive electrode externally connectingland 12 and a negative electrode externally connecting land 13 aredirectly provided on each of insulating substrates 3 and 32, withexternally connecting wires 14 used for electrically connecting thesepositive electrode externally connecting land 12 and negative electrodeexternally connecting land 13 to a power supply (not shown) beingprovided thereto.

Moreover, as shown in each of FIGS. 1 and 4 to 7, the light emittingdevice of the present invention is preferably designed to have astructure in which external wiring holes 15 which allow externallyconnecting wires 14 to pass through are formed on each of insulatingsubstrates 3 and 32. In the examples shown in FIGS. 1 and 4, oninsulating substrate 3 having a square top shape, positive electrodeexternally connecting land 12 and negative electrode externallyconnecting land 13 are provided to be disposed on another diagonal linethat is different from the diagonal line on which the aforementionedsecuring holes 11 are provided, and external wiring holes 15, eachhaving a cut-out shape, are formed on opposing two sides near the centerthereof of insulating substrate 3. Moreover, in the examples shown inFIGS. 5 to 7, on insulating substrate 32 having a round top shape,externally wiring holes 15, each having a cut-out shape, are formed on astraight line that passes through the center and is substantiallyperpendicular to the straight line passing through the center on whichsecuring holes 34 are formed as described above, and positive electrodeexternally connecting land 12 and negative electrode externallyconnecting land 13 are each formed between securing holes 34 andexternally wiring holes 15 so as to be made face to face with eachother. It should be noted that, as shown in each of the examples ofFIGS. 4 to 7, in the case where securing holes 34 and externally wiringholes 15 are formed as cut-out sections on insulating substrate 32having a round top shape, the resulting structure also exerts arotation-stopping function for preventing the light emitting device fromrotating in a circumferential direction in a state of being attached toa matching member.

Moreover, as shown in FIG. 3, the light emitting device of the presentinvention is preferably designed to have a structure in which oninsulating substrate 3, externally lead-out wiring patterns 16 and 17that electrically connect ends of wiring patterns 4 to positiveelectrode externally connecting land 12 and negative electrodeexternally connecting land 13 are further formed. By using theseexternally lead-out wiring patterns 16 and 17, the power supply (notshown) and wiring patterns 4 can be electrically connected to each otherthrough positive electrode externally connecting land 12 and externallylead-out wiring pattern 16, and negative electrode externally connectingland 13 and externally lead-out wiring pattern 17.

Moreover, the light emitting device of the present invention ispreferably provided with an inspecting pattern formed on the insulatingsubstrate. FIG. 3 shows an example in which spot-shaped inspectingpatterns 18 are formed between a wiring pattern 4 a and a wiring pattern4 b as well as between a wiring pattern 4 c and a wiring pattern 4 d. Byforming these inspecting patterns 18 on insulating substrate 3,conduction inspecting processes between wiring pattern 4 a and wiringpattern 4 b, between wiring pattern 4 b and wiring pattern 4 c, as wellas between wiring pattern 4 c and wiring pattern 4 d, can be easilycarried out by using inspecting patterns 18. Moreover, these inspectingpatterns 18 may also be used as recognition patterns to be used incarrying out die bonding and wire bonding processes by an automationapparatus. It should be noted that the inspecting pattern is not limitedto the spot-shaped pattern as shown in FIG. 3, and it may be prepared asa pattern that is electrically connected to both wiring pattern 4 b andwiring pattern 4 c and has a size that allows a probe to be made incontact therewith.

The present invention also provides a method for manufacturing a lightemitting device. Although the method for manufacturing theabove-mentioned light emitting device of the present invention is notparticularly limited, it is suitably manufactured by using the methodfor manufacturing a light emitting device of the present invention. Themethod for manufacturing a light emitting device of the presentinvention basically includes a process for forming wiring patterns on aninsulating substrate, a process for mounting a light emitting elementbetween wiring patterns, a process for electrically connecting the lightemitting element and the wiring patterns, a process for placing asilicone rubber sheet having a through hole onto the insulatingsubstrate, and a process for forming a sealing member for sealing thelight emitting element in the through hole of the silicone rubber sheet.FIG. 11 is a diagram showing processes for manufacturing light emittingdevice 1 shown in FIG. 1 step by step, as one preferred example of amethod for manufacturing a light emitting device of the presentinvention. Referring to FIG. 11, the method for manufacturing the lightemitting device of the present invention will be discussed in detail inthe following description.

First, as shown in FIG. 11(a), wiring patterns 4 are formed on aninsulating substrate 3. As described above, since FIG. 11 shows the casein which light emitting device 1 shown in FIG. 1 is manufactured, fourlinear wiring patterns 4 a, 4 b, 4 c, and 4 d are disposed in parallelwith one another on insulating substrate 3, as wiring patterns 4. In onepreferable specific example, on white insulating substrate 3 made ofaluminum oxide having a thickness of 1 mm, a gold film having athickness of 0.07 mm is formed by using a sputtering method, and wiringpatterns 4 a, 4 b, 4 c, and 4 d (1 mm in width, at 2 mm intervals) arethen formed thereon by a photo-etching method; however, the presentinvention is not limited by this method. In the case of forming apattern that is expanded outwards from a straight line as a pattern 7for use in positioning electrical connections with light emittingelements or for use as a measure for mounting positions of the lightemitting elements, externally lead-out wiring patterns 16 and 17 and aninspecting pattern, desired patterns may be designed and subjected tophoto-etching processes.

Next, as shown in FIG. 11(b), each of light emitting elements 5 ismounted between wiring patterns 4. The mounting of each light emittingelement 5 can be carried out by directly bonding the light emittingelement 5 to insulating substrate 3 using a thermosetting resin such asan epoxy resin, an acrylic resin and an imide resin. With thisarrangement, the dielectric voltage, which is determined by the creepingdischarge voltage, can be made as high as possible. That is, thedielectric voltage between the light emitting elements that are arrangedin the electrode direction is determined by the distance between thelight emitting elements and the dielectric constant of the insulatingsubstrate, and the dielectric voltage between the light emitting elementand the electrode is also determined by the shortest distance betweenthe light emitting element and the electrode and the dielectric constantof the insulating substrate. In a preferable specific example, a LEDchip having a short-side width of 0.24 mm, a long-side width of 0.48 mm,and a thickness of 0.14 mm is bonded to each of gaps between linearwiring patterns 4 a, 4 b, 4 c, and 4 d that are formed on insulatingsubstrate 3 in parallel with one another, and secured therein, as lightemitting element 5, by using an epoxy resin; however, the presentinvention is not limited thereto. Thereafter, as shown in FIG. 11(b),wiring patterns 4 and light emitting elements 5 are electricallyconnected with one another by using wire bonding W, in accordance with adesired state of electrical connection.

It should be noted that the method for manufacturing a light emittingdevice of the present invention preferably further includes a processfor inspecting the characteristics of the light emitting elements afterthe above-mentioned electrical connection between the light emittingelements and the wiring patterns is made, and a process in which, upondetection of any defect in characteristics, a spare light emittingelement is connected to the wiring patterns. This inspection can becarried out, for example, by flowing an electric current through thelight emitting element so as to measure the optical outputcharacteristics. Moreover, disconnection of bonding wire W and bondingdefect may be checked in external appearance inspecting processes at thesame time.

Next, as shown in FIG. 11(c), a silicone rubber sheet 91 having athrough hole 92 is placed on insulating substrate 3. FIG. 12 is adiagram schematically showing silicone rubber sheet 91 as one preferredexample to be used in the method for manufacturing a light emittingdevice of the present invention. The silicone rubber sheet to be used inthe manufacturing method of the present invention has a through hole forproviding a space in which the sealing member is formed, and the shapeof the through hole is not particularly limited and may be formed intoany shape in accordance with the top shape of a sealing member to beformed. As described earlier, since the sealing member is preferablyformed to have a top shape such as a hexagonal shape, a round shape, arectangular shape, and a square shape, the through hole of siliconerubber sheet 91 is preferably formed to have the corresponding top shapesuch as a hexagonal shape, a round shape, a rectangular shape, and asquare shape. For example, FIG. 12 shows silicone rubber sheet 91 with athrough hole 92 having a rectangular shape in top view. It should benoted that the silicone rubber sheet 91 having the above-mentionedthrough hole 92 is suitably used in a case in which all the linearwiring patterns and light emitting elements on the insulating substrateare sealed by a single sealing member; however, in the case where aplurality of linear sealing members are formed in such a manner as toinclude light emitting elements 5 mounted on the two sides along thelinear wiring patterns 4, a silicone rubber sheet having a plurality ofthrough holes with the desired corresponding shapes may be used.

Silicone rubber sheet 91, which is easily available and has anelasticity because it is made of rubber, is preferably used because itcan be provided in a tightly contact state without a gap even when thereis a difference in the form of a step in wiring patterns and the like.Moreover, to one of the surfaces of silicone rubber sheet 91, adouble-sided bonding sheet is preliminarily bonded, since it can preventleakage of resin used for forming the sealing member in the state ofbeing disposed on insulating substrate 3, which will be described later,and since it is easily removed after formation of the sealing member,and silicone rubber sheet 91 is preferably bonded to insulatingsubstrate 3 by this bonding sheet.

The silicone rubber sheet to be used in the method for manufacturing alight emitting device of the present invention is preferably designed tohave a thickness that is two or more times thicker than the thickness ofthe first sealing member layer to be formed. By allowing the siliconerubber sheet to have two or more times thicker than the thickness of thefirst sealing member layer, it becomes possible to carry out a doublecoating process to correct chromaticity shifts, and consequently toprevent leakage of the sealing material.

Next, as shown in FIG. 11(d), sealing member 6 used for sealing lightemitting elements 5 is formed in through hole 92 of silicone rubbersheet 91. Sealing member 6 preferably contain a fluorescent material, asdescribed earlier. Moreover, sealing member 6 may be formed as either asingle layer or two layers (since FIG. 11 shows processes formanufacturing light emitting device 1 shown in FIG. 1, sealing member 6is formed to include a first sealing member layer 8 containing a firstfluorescent material and a second sealing member layer 9 containing asecond fluorescent material).

The process for sealing the light emitting elements by using thissealing member in the method for manufacturing a light emitting deviceof the present invention preferably includes a process for injecting asealing material containing a first fluorescent material into thethrough hole of a silicone rubber sheet, a process for curing thesealing material containing the first fluorescent material to form afirst sealing member layer, and a process for measuring a chromaticitycharacteristic of the light emitting device after the first sealingmember layer is formed.

In this case, first, the sealing material containing the firstfluorescent material is injected into through hole 92 of silicon rubbersheet 91. With respect to the sealing material, as described earlier,preferable examples include light-transmitting resin materials superiorin weather resistance, such as an epoxy resin, a urea resin and asilicone resin, and light-transmitting inorganic materials, such assilica sol and glass, superior in resistance to light. Moreover, withrespect to the first fluorescent material, as described earlier,preferable examples include: Ce:YAG fluorescent material, Eu:BOSEfluorescent material or Eu:SOSE fluorescent material, andeuropium-activated α-sialon fluorescent material. Moreover, theaforementioned dispersing agent may be added to the sealing material.

Next, the sealing material containing the first fluorescent material,injected into through hole 92 of silicone rubber sheet 91, is cured. Themethod for curing the sealing material is not particularly limited, andany conventionally known method may appropriately be used in accordancewith the sealing material to be used. For example, in the case where asilicone resin that is a light-transmitting resin material is used asthe sealing material, the sealing material can be cured by thermallycuring the silicone resin. It should be noted that a resin for use inmolding may be used as the sealing material, and the sealing materialmay be cured by using a metal mold. The shape of the sealing member (thefirst sealing member layer) to be formed by curing the sealing materialis not particularly limited, and for example, a sealing member having asemi-spherical shape with an upward convex portion may be made so thatthe sealing member is allowed to function as a lens.

Next, the chromaticity characteristics of the light emitting devicehaving the first sealing member layer formed thereon as described aboveare measured. FIG. 13 is a graph that shows chromaticity coordinates ofCIE (Commission Internationale del'Eclairage). The chromaticitycharacteristics of the light emitting device can be measured by using ameasuring device which uses an optical system of d·8 (diffusedlighting·8°: light-receiving system) in accordance with DIN5033teil7,ISOk772411 under the condition C of JIS Z 8722. For example, in the casewhere, in order to obtain light that corresponds to x, y=(0.325, 0.335)on the CIE chromaticity diagram, a material prepared by mixing the firstfluorescent material and a silicone resin serving as the sealingmaterial at a weight ratio of 5:100 is injected into through hole 92 ofsilicone rubber sheet 91, and thermally cured at 150° C. for 30 minutesto form the first sealing member layer, the chromaticity range of thefirst sealing member layer thus formed is located within a region (a) inFIG. 13. In the case of measuring chromaticity characteristics of thelight emitting device having the first sealing member layer of thiskind, the chromaticity range goes out of the region (b) in FIG. 13. Insuch a case, a second sealing member layer is formed on the firstsealing member layer so that the chromaticity range of the lightemitting device is located within the region (b) in FIG. 13.

In the case where the second sealing member layer is formed, the methodfor manufacturing a light emitting device of the present inventionpreferably further includes the following processes after theabove-mentioned process for measuring the chromaticity characteristicsof the light emitting device after the formation of the first sealingmember layer: a process for pouring a sealing material containing asecond fluorescent material onto the first sealing member layer, aprocess for curing the sealing material containing the secondfluorescent material to form a second sealing member layer, a processfor measuring chromaticity characteristics of the light emitting deviceafter the formation of the second sealing member layer, and a processfor removing the silicone rubber sheet. That is, in the same manner asin the respective processes for forming the above-mentioned firstsealing member layer, first, the sealing material containing the secondfluorescent material is poured onto the first sealing member layer, andcured thereon to form the second sealing member layer. The secondfluorescent material and sealing material used for forming the secondsealing member layer are appropriately selected from the firstfluorescent material and sealing materials used for forming theaforementioned first sealing member layer, in accordance with desiredchromaticity characteristics, and may be prepared by further adding adispersing agent thereto in some cases. In the above-mentioned case, inorder to obtain light that corresponds to x, y=(0.345, 0.35) on the CIEchromaticity diagram, for example, a material prepared by mixing thesecond fluorescent material and a silicone resin serving as the sealingmaterial at a weight ratio of 2:100 is poured onto the first sealingmember layer, and thermally cured at 150° C. for one hour to form thesecond sealing member layer. With this arrangement, in the case ofmeasuring likewise the chromaticity characteristics of the lightemitting device after the formation of the second sealing member layer,the resulting light emitting device can have a chromaticity range thatis located within the region (b) in FIG. 13.

In this manner, by further forming the second sealing member layer asneeded, the method for manufacturing a light emitting device of thepresent invention makes it possible to manufacture a light emittingdevice free from chromaticity shifts at a low cost with a high yield. Itshould be noted that, as described above, it is only necessary for thesecond sealing member layer to cover at least one portion of the upperface of the first sealing member layer, and it may cover the entireupper face of the first sealing member layer (for example, the examplesshown in FIGS. 1, 4, and 5), or may partially cover the upper face ofthe first sealing member layer (for example, the examples shown in FIGS.6 and 7).

Moreover, for example, in the case where, in order to obtain light thatcorresponds to x, y=(0.325, 0.335) on the CIE chromaticity diagram, amaterial prepared by mixing the first fluorescent material and asilicone resin serving as the sealing material at a weight ratio of 5:80is injected into through hole 92 of silicone rubber sheet 91, andthermally cured at 120° C. for 30 minutes to form the first sealingmember layer, in measuring the chromaticity characteristics of the lightemitting device after the formation of the first sealing member layer,the chromaticity range thereof is located within the region (b) in FIG.13; therefore, in this case, it is not necessary to further form theaforementioned second sealing member layer, and the light emittingdevice having the first sealing member layer as it is as the sealingmember may be manufactured.

In the method for manufacturing a light emitting device of the presentinvention, as described above, after the first sealing member layeralone has been formed, or after the first and second sealing memberlayers have been formed, silicone rubber sheet 91 is removed, so thatthe light emitting device of the present invention is provided. Asdescribed earlier, silicon rubber sheet 91 may be prepared with atwo-sided bonding sheet being preliminarily bonded to one of the facesthereof, and then bonded to insulating substrate 3 by using this bondingsheet; thus, silicone rubber sheet 91 can easily be removed. It shouldbe noted that the silicone rubber sheet can be used repeatedly.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

1. (canceled)
 2. A light emitting device comprising: a substrate havinga top surface and a bottom surface opposite from the top surface, thesubstrate including a lighting area and a peripheral area surroundingthe lighting area in the top surface of said substrate; a positiveelectrode land for external connection on the top surface and a negativeelectrode land for external connection on the top surface, said positiveand negative electrode lands being provided on the peripheral area ofsaid substrate; a light emitting unit formed on the lighting area ofsaid substrate, including a plurality of light emitting elements, and asealing member for sealing and covering the plurality of light emittingelements, the sealing member being located within the lighting area,wherein the sealing member includes a first sealing member layercontaining a first fluorescent material and a second sealing memberlayer that contains a second fluorescent material that is different fromthe first fluorescent material.
 3. The light emitting device of claim 1,wherein the shape of the upper face of sealing member is hexagonalshape, a round shape or a rectangular shape.
 4. The light emittingdevice of claim 1, wherein the shape of the upper face of the substrateis a round shape or a rectangular shape.
 5. The light emitting device ofclaim 1, wherein the substrate includes a positive polarity markadjacent to the positive electrode land.
 6. The light emitting device ofclaim 4, wherein the substrate includes a negative polarity markadjacent to the negative electrode land.
 7. The light emitting device ofclaim 1, wherein the substrate includes a negative polarity markadjacent to the negative electrode land.
 8. The light emitting device ofclaim 1, further comprising wiring patterns, wherein wiring patternsinclude a cathode wiring pattern and an anode wiring pattern disposed onthe top surface of said substrate and connected to said positive andnegative electrode lands, respectively.
 9. The light emitting device ofclaim 7, wherein the positive electrode land is connected to the anodewiring pattern through lead-out wiring patterns, and the negativeelectrode land is connected to the cathode wiring pattern throughlead-out wiring patterns, and wherein lead-out wiring patterns include afirst lead-out wiring pattern that is formed between the positiveelectrode land and the anode wiring pattern, and a second lead-outwiring pattern that is formed between the negative electrode land andthe cathode wiring pattern.
 10. The light emitting device of claim 1,wherein the second sealing member layer is formed on the first sealingmember layer.
 11. The light emitting device of claim 9, wherein thesecond sealing member covers at least one portion of the first sealingmember layer.